Concurrent engineering of a next-generation freeform telescope: mechanical design and manufacture

This manuscript is the second of three submissions to describe the concurrent engineering of a 250 mm aperture class three mirror anastigmatic (TMA) visible spectrum imager. The system is an off axis, F/3, 3 degree FOV imager with all freeform mirrors. The major drivers for the mechanical design were low mass, stiffness, robustness, thermal stability, and scalablility. The system is designed using silicon carbide (SiC) for the optics and housing to meet these requirements. The scope of this manuscript is limited to aluminum prototype optics, which are identical to the SiC components. Here, we describe the mechanical design process to light weight the optics while maintaining adequate stiffness. Also described is the pairing of the optic with an optical cell for both the manufacture and system integration using kinematic mounts. The mount design pairs with a matched kinematic mount for off machine figure metrology. This allows for an iterative figure convergence process. A design for manufacture and metrology approach was used to ensure the system elements can be both manufactured and measured by providing feedback to the optical designers.